In packet switched networks such as the Internet, Quality of Service (QoS) generally refers to the ability to provide different priority to different applications, users, or data flows, or to guarantee a certain level of performance to a data flow. For example, a required bit rate, delay, jitter, packet dropping probability and/or bit error rate may be guaranteed for a particular application. Quality of service guarantees may be important if, for example, network capacity is limited and in particular for real-time streaming multimedia applications such as voice over IP (VoIP), online games and IP-TV, because these often require a minimum fixed bit rate and are delay sensitive. QoS may also be needed in networks where bandwidth is a limited resource, for example in cellular data communication. This disclosure is directed to improving QoS in networks.